1. Field of the Invention
The present invention relates to methods and compositions for the loosening and subsequent removal of lice egg infestations from the hair and scalp.
2. Description of the Prior Art
Throughout history, human beings in all parts of the world have suffered from parasitical infestations, including infestations of the hair and scalp by head lice (Pediculus humanus var capitis). Many methods of treating such head louse infestations have been proposed and utilized for centuries including, for example, washing the head with strong soaps and lye and the utilization of kerosene to kill adult lice and their ova. In more recent times, various ectoparasiticides have been incorporated into creams, gels, shampoos and the like for application to human hair and scalp.
Some of the ectoparasiticides which have been utilized as pediculicidal treatments since the early 1950s and are commercially available today in various forms include the insecticides lindane and malathion, as well as pyrethrins (chrysanthemin carboxylic esters of pyrethrolone), derived from certain variants of the chrysanthemum family. Compositions containing pyrethrins as active ingredients normally include, in addition, a pyrethrin synergist such as piperonyl butoxide which greatly enhances pediculicidal activity. See, generally, Journal of the American Medical Association, Vol. 247, No. 22, pp. 3103-05 (Jun. 11, 1982), for a description of various pediculicidal agents and compositions.
One of the serious drawbacks of the commonly utilized compositions for treatment of head louse infestations is that while many of them are highly effective against the adult parasites, and some produce significant mortality rates among louse ova as well, they leave a substantial number of ova intact after treatment. These lice eggs or nits cling tenaciously to the hair shafts, usually close to the scalp, because they are surrounded by a layer of chitinous material that acts as a xe2x80x9cnit cement.xe2x80x9d If they are not physically removed from the subject""s hair, they may simply hatch after a period of time and cause re-infestation.
Among the techniques conventionally used to remove the lice eggs after treatment of a subject""s hair and scalp with pediculicidal agents are the vigorous brushing of the hair, combing with a fine tooth nit comb or the use of implements such as tweezers, pencils or sharpened sticks to remove the nits individually from the hair shafts, usually with the aid of a bright light and some form of optical magnification. These techniques are time-consuming, inefficient and rarely succeed in removing substantially all of the remaining lice eggs because they are firmly adhered by the cement to the hair.
Lice ova removal or loosening compositions to be applied to the hair have been proposed in the prior art. For example, U.S. Pat. No. 5,557,665 discloses the application of an enzyme composition to the hair, said composition comprising a water-based enzyme and a stabilizer. The enzyme causes the swelling and/or breakdown of the nit cement to facilitate the subsequent removal of the nits from the hair. Such enzyme compositions are, however, relatively difficult to manufacture and are expensive for consumers, who are frequently non-wealthy parents of young children. Moreover, it is not clear that such compositions are substantially more effective than the physical removal techniques that have been practiced traditionally in the prior art.
Hence, there is a need for improved compositions and methods to remove lice ova from the hair and scalp of an infested subject.
1. Objects of the Invention
It is an object of the present invention to provide compositions which may be applied to the hair and scalp of human subjects, or to other hairy body areas, and which are effective in loosening and removing lice ova or nits therefrom.
An additional object of the present invention is to provide compositions as described above which are safe, easy to use and relatively inexpensive.
A further object of the present invention is to provide compositions as described which are not enzyme based.
Yet another object of the present invention is to provide compositions as described above which also include active pediculicidal and/or ovicidal ingredients.
Still another object of the present invention is to provide a method of loosening lice ova from the hair of a human subject by applying compositions as described above.
Yet a further object of the present invention is to provide a kit that can be used to perform the method of the invention.
2. Brief Description of the Invention
In keeping with these objects and others which will become apparent hereinafter, the present invention resides, in a first aspect, in compositions for removal of lice ova or nits from the hair of human subjects. The novel nit removal compositions comprise from about 1 to about 50% by weight of dimethyl isosorbide in an aqueous vehicle having a neutral to acidic pH. The compositions can be in any suitable physical form, but are preferably in the form of a gel or liquid.
The phrase xe2x80x9c% by weightxe2x80x9d used throughout this specification and the appended claims refers to the percentage of the weight of the total composition constituted by the specified component or ingredient.
The invention also comprehends in a second aspect a method of loosening lice ova from the hair or scalp of a human subject, or from other hair/body areas, by applying compositions as described above to the hair or scalp of the subject and subsequently rinsing off with water, with the remaining nits being combed out with a fine tooth comb.
In a third aspect, the invention comprehends kits for use in practicing the method of the invention, said kits containing a composition according to the invention and a nit comb.